The scope of reproductive research within this ORPRC project emphasizes: 1) transport, maturation, and storage of sperm, and the structure and function of the epididymis; 2) long-term effects of vasectomy: autoimmune response; 3) the enzymic and hormonal regulation of energy metabolism in ejaculated and maturing spermatozoa; 4) the hormonal regulation of the life cycle and dynamics of the epithelium of the oviduct; 5) receptor proteins in the oviduct and uterus; 6) the relationship of ovarian steroid secretion to follicular growth, ovulation and local steroid changes in reproductive tissues; 7) the role of estrogens and androgens in the regulation of gonadotropins; 8) blood flow in the reproductive organs and its relation to prostaglandins; 9) the role of androgens and estrogens in sexual behavior and psychosexual differentiation; 10) factors that regulate the motivation of sexual behavior; 11) the role of light on sexual cycles.